Therefore, IgM serology does not always appear useful for diagnostic purposes of active SARS-CoV-2 infection, while IgG serology has been suggested to be used for three purposes in the SARS-CoV-2 pandemic: (1) to diagnose infection in a limited niche of patients, (2) to identify convalescent plasma donors, and (3) to screen populations with the purpose to determine exposure and immunity [34]. Here, CD40LG is linked to infection.